Ansible tasks should be idempotent. Eg. if the task does not modify anything, it should return ok instead of changed. Most builtin modules and tasks are already, but for tasks such as command and shell you need to help ansible a bit.
For a task that does purely checking and does not modify anything, you should add:
changed_when: False always_run: yes The latter allows the task to run even in check mode.
For the sake of completeness, such tasks are usually combined with another that does the actual modification, eg:
- command: check command that returns true when no change needed register: result changed_when: False always_run: yes - command: modify command when: result.rc != 0